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Commit 7cb671e7 authored by Alex Williamson's avatar Alex Williamson
Browse files

vfio/type1: Reduce repetitive calls in vfio_pin_pages_remote() 



vfio_pin_pages_remote() is typically called to iterate over a range
of memory.  Testing CAP_IPC_LOCK is relatively expensive, so it makes
sense to push it up to the caller, which can then repeatedly call
vfio_pin_pages_remote() using that value.  This can show nearly a 20%
improvement on the worst case path through VFIO_IOMMU_MAP_DMA with
contiguous page mapping disabled.  Testing RLIMIT_MEMLOCK is much more
lightweight, but we bring it along on the same principle and it does
seem to show a marginal improvement.

Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Reviewed-by: default avatarKirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 80dbe1fb

drivers/vfio/vfio_iommu_type1.c

+11 −6
Original line number Diff line number Diff line
@@ -380,10 +380,10 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, 
 * first page and all consecutive pages with the same locking.

 */

static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,

				  long npage, unsigned long *pfn_base)

				  long npage, unsigned long *pfn_base,

				  bool lock_cap, unsigned long limit)

{

	unsigned long pfn = 0, limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

	bool lock_cap = capable(CAP_IPC_LOCK);

	unsigned long pfn = 0;

	long ret, pinned = 0, lock_acct = 0;

	bool rsvd;

	dma_addr_t iova = vaddr - dma->vaddr + dma->iova;
@@ -924,13 +924,15 @@ static int vfio_pin_map_dma(struct vfio_iommu *iommu, struct vfio_dma *dma, 
	unsigned long vaddr = dma->vaddr;

	size_t size = map_size;

	long npage;

	unsigned long pfn;

	unsigned long pfn, limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

	bool lock_cap = capable(CAP_IPC_LOCK);

	int ret = 0;



	while (size) {

		/* Pin a contiguous chunk of memory */

		npage = vfio_pin_pages_remote(dma, vaddr + dma->size,

					      size >> PAGE_SHIFT, &pfn);

					      size >> PAGE_SHIFT, &pfn,

					      lock_cap, limit);

		if (npage <= 0) {

			WARN_ON(!npage);

			ret = (int)npage;
@@ -1040,6 +1042,8 @@ static int vfio_iommu_replay(struct vfio_iommu *iommu, 
{

	struct vfio_domain *d;

	struct rb_node *n;

	unsigned long limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

	bool lock_cap = capable(CAP_IPC_LOCK);

	int ret;



	/* Arbitrarily pick the first domain in the list for lookups */
@@ -1086,7 +1090,8 @@ static int vfio_iommu_replay(struct vfio_iommu *iommu, 


				npage = vfio_pin_pages_remote(dma, vaddr,

							      n >> PAGE_SHIFT,

							      &pfn);

							      &pfn, lock_cap,

							      limit);

				if (npage <= 0) {

					WARN_ON(!npage);

					ret = (int)npage;